rotary engines: advantages
 

i'm wondering why i never saw a comparison of advantages of rotaries to pistons?
are they that obvious, or people just love it sooo much that they don't care?
at any rate, this will be some good read and leaves room for some more input.
PROS:
1)no timing belt to change
2)no sudden catastrophic failure from snapped belt compared to a timing belt equipped piston motor
3)less moving parts
4)no valve adjustment or other attached maintenance than regular routing maintenance
5)light weight

cons:
1)high oil consumption
2)high fuel consumption
3)more frequent ignition component maintenance
4)

please feel free to add. i'd like to see where the list stops.

and someone should sticky this, i'm tires of noobs coming in with "rx-8 vs S2k, which should i get?" posts. let them see the pros/cons for themselves

:yelrotflm

where do you get that popcorn, i cant find it in the smileys

Pro:
longer torque band.

its not a massive amount of torque but theres a longer band along the revs

another Pro: high revving

Are you talking about our spark plugs ? :)

thanks

yes. but it wouldn't only be that now.

doesn't seem to be a highlighted point or boasted about often. but o well...its still impressive for its given size.

high revving...yes, that one is good.

:yelrotflm what? you can't gather any thoughts?

pros and cons.

supply them. whats it to you?

have you seen the constant lame questions of car comparisons posts by noobs?

i'd have to agree that rotaries are NOT for everyone. and if you are clear on the pros/cons of it, then make your decision on such...its like no-one bothers to get a friggin brochure nowadays.

so yeah, any pros/cons you'd like to supply?

pro: high exhaust flow and temperatures!

just how is that a pro? with all seriousness...

i know one power stroke/exhaust stroke every crank revs. or 3 crank rev for every one rotor revolution... but what are the exact advantage of having high temps?

and is that what you would like to state as an advantage if you were promoting the facts of this motor?

it enables for a small engine like the 1.3L renesis to use a reasonably large turbo with basically no lag time

i see. that must've blew right by me. thanks.

....

http://i34.photobucket.com/albums/d1...ad/popcorn.gif + 1 (Thanks Darkbrew...!)

pro ---- small. adn takign out one involves 2 people and a small wrench.

no seriously. thats it ......... no wenches, etc..

Gives you an excuse to say wankle in polite company.

Pro: It goes "Hmmmmm"
Pro: It doesn't go "BOING BOING BOING"

http://www.mazdamaniac.com/portal/smiles/doobie.gifhttp://www.mazdamaniac.com/portal/smiles/popcorn3.gifhttp://www.mazdamaniac.com/portal/smiles/spew.gifhttp://www.mazdamaniac.com/portal/smiles/yumyum.gif

Hmm, should I have an engine with over a thousand moving parts—or three? Gee, that's a tough one.

The big advantage of the rotary is… feel & handling. The tiny, lightweight Renesis–barely 13" tall—allows a near mid-engine design and a 50/50 weight balance—the secret behind the 8's remarkably lively feel, agility and handling.

yes, and contributing to a lower yaw and pmoi. i added that in there already. you just said it better. but thanks anyway.

the biggest pro for the rotary isn't for cars, it's for airplanes:

reliability thru simplicity: it won't fail catasthophically because it's perfectly balanced. Even if it blows a seal or it misfires or the oil runs out, if you have a problem the engine will still make some form of power for an amount of time, enough to get you that little extra distance and quite possibly save your life.

A piston engine that throws connecting rod or something of the like will literally tear itself to pieces, immediately lose all power and depending on the damage even eject pistons or other parts out the side of the aircraft.

it's also quieter and the frontal profile is much much smaller that lets you design more aerodynamically.

but there are still tradeoffs, you need to water cool it and you need a gearbox to get the engine revs down to normal prop operating speeds so the weight advantage doesn't exist.

interesting newfound information... cool stuff. i can see the other advantages of rotaries being in aairplanes.

am i the ONLY one who read more out of this then just the words?

Your with the rest of us Paul....if a picture paints a thousand words we're done here...:boring:

lol.

OK i think this is the pendulum for the 'wankel'.

The ability to run Hydrogen fuel on the fly. If storage and efficiency can be doubled, then this will lead the way for city driving. Realistically, you don't need 240hp in heavy city areas.

OPEC loves it. Advantage OPEC. Can you imagine OPEC having a circle jerk right now if the world was running on rotaries? Then again, its development would be much further along.

Probably not. Just the first, I'd think.

Well, if you are going to count the thousand minor moving parts in a piston motor instead of just the 30 or so major ones, than you need to count all 75 or so of the moving parts on the rotary as well.

^^oh no! MM's gonna tell him the truth now. he's gonna tell him our cars DO have valves.

don't do it, he'll probably kill himself if he's never had a piston car before... ;) :wink2:

ehhh, at least i'm not alone. its quite common in my workplace that i perceive things in a different manner than anyone else. guess its the libido, lol

Well, technically, we do have valves. There are at least three in the LIM alone.
They are just not tied to the combustion period.

:doh: awww.... don't rotor heads hate that dreaded word, valves?
its like using pistons, con-rods, crank bearings, camshafts, lifters, piston rings, springs all in one sentence.:doh:

Or cutoff rings, side seals, corner seals, apex seals, oil seals or seal springs in one sentence.

I'll tell you what I like about rotaries - no crappy mechanical noises like tappet or cam chain rattles . I really hate those noises

What I like about some piston motors : They can be visual works of art - take a look at a bliged out EVO or s2000 motor - sexy . Then have a look at a renesis - real hard to get it to look anything at all - mainly because it is hidden by rubber hoses and plastic manifolds

The only way to make a rotary pretty is to strip it naked and strap a giant turbo on it.
The keg is just not something to look at and all the ancillaries are not aesthetically pleasing.

I do agree on the noises. I find myself listening for the faint "swish" of the side seals when the motor is cold.
The motor is so inherently quiet, that the mild tapping of the evap solenoid sounds like a cattle stampede by comparison.

Actually, it's an old Mazda commercial for... what was it, the RX-3? "And the Mazda goes 'Hmmmmmmm.....'". Catchy little theme.

Someone has been reading! Awesome.

Everyone mentioned pros, I'll go the other way round (at the cost of being flamed ;) ) and add:

cons: higher emissions (at least CO2)

the rotary is alot smoother than conventional piston engines cause of the less moving parts in the engine.

plus our 1.3L can compete w/ some decent sized V6's but weight a whole lot less and still produce the same amount of HP

online. not those books yet, they still havent come. im going to call amazon and bitch them out

Nice new avatar pic Kane...are we ever going to see that 'Arnie' crossed arms shot again...?

If you include every seal in a 2 rotor engine, the total number of parts are as follows. Keep in mind I'm only referring to moving parts. Stationary gears and bearings don't move.

apex seals: 6
apex seal springs: 12
corner seals: 12
corner seal springs: 12
side seals: 12
side seal springs: 12
oil seals: 8
oil seal springs: 8
cutoff seals: 4
cutoff seal springs: 4
rotors: 2
eccentric shaft: 1

That's 93 parts. Major moving parts however only equals 3 as seals are not considered major moving parts.

In a 1 cylinder engine by comparison, not counting seals you could have:

piston: 1
connecting rod: 1
crankshaft: 1
valves: 2-4 (and even up to 5 on rare occasions)
valve springs: 2-4 (5)
camshaft: 1-2

That alone is anywhere from 8-13 major moving parts assuming it's an overhead cam engine per cylinder. That's not including any seals, rings, wrist pins, etc. A non overhead valve engine would add pushrods and rocker arms at a minimum.

The rotary always has fewer moving parts than a piston engine. There's no way around this. You can count every single little part inside the rotary and add them up but at the end of the day the number of major moving parts that exert any appreciable force from mass on anything only equals 3. 2 rotors and 1 eccentric shaft. This is a huge rotary advantage. Fewer parts means simplicity and that's a wonderful thing.

Another advantage is power per size of package. The rotary is very compact. A manifold doesn't have to be big and bulky. It can be very simple an compact which is why it's a great small airplane engine.

The fact that it is physically small also means that it's center of gravity is over a very small total area in both horizontal and vertical directions. That's an advantage for many reasons from packaging to handling.

No the rotary isn't a perfect engine. There isn't any one engine that can claim this title. For it's size it's far more impressive than many very popular engines though. Even the great LS1 is nothing special. It doesn't really produce an impressive amount of power for it's displacement and can't be held at high rpms for extensive amounts of time at high loads. If you don't believe me then go look up small airplane conversions that have used these engines. They ALL fail spectaularly. The only reason that engine does what it does is due to it's size. They kept weight relatively low by building it out of aluminum and it's plentiful. Americans go crazy over V8's. You could build a crap one and it would sell. Ford does it all day everyday.

The point of this is to show that although the rotary has it's negatives, you really need to appreciate and respect what it does for what it is. It's simplicity and small size are impressive compared to many others. If it were all aluminum, there wouldn't be another engine of it's weight out there that could produce the same amount of power. It's not perfect but it's got advantages. Those that think it doesn't really have no clue and should best be left alone to grow their mullets and build their overly large and heavy engines.

Pro: Elegance
Con: Frailty brought on by elegance

My rotors don't move. The rest of the world spins around them.

oooo, good one ^

The one of me and my son you mean?

I was told that my wifes pics were more appreciated - HAHA

Not sure if you can count this. You obviously haven't been around sport bike engines, have you? Give a piston motor a decidedly over-square build (big bore, short stroke), fill it with strong, lightweight internals, and you have a recipe for a 17,500 rpm redline, which the current Yamaha YZF-R6 600cc in-line 4 cylinder has.

Honda also had a quad-carbed 600cc in-line 4 cylinder race motor back in the late 70's they stuffed in some of their Nighthawk's and other bikes for racing that revved to 23,000 rpm.

Miniature R/C cars that use 2-stroke nitro-burning single cylinder, air-cooled .12-.21cc motors can rev to over 60,000 rpm as well, and idle at over 6,000 rpm!




Beyond all that, surprised no one mentioned this Pro; It's unique!

I know R/C cars's engine go crazy on RPM, you think I've never play with HPI before? :) I still have them and that little bastard runs fast (it run faster than my 8, in the first 1-2 seconds LOL)
but when you talking about the same purpose theres not much competition. :)

I have also read that since rotaries love being revved, you can run them closer to max throttle for longer periods of time then piston engines (which are designed only to provide peak power for short periods during acceleration).